1. Field of the Invention
The present invention relates to a method, a computer, and a program for calculating engine design variables. More specifically, it relates to a method, a computer, and a program for optimizing a degree of change (smoothness) of design variables in relation to the change of operating states when calculating global optimal solutions of the design variables (e.g., EGR valve position, fuel injection timing, ignition timing, and the like) which minimize or maximize a combination of multiple objective variables (e.g., specific fuel consumption, nitrogen oxides emission concentration) for multiple combinations (modes) of multiple operating states (e.g., engine revolutions, loads, and the like) included in an operating range of the engine.
2. Related Art
Conventionally, various methods have been proposed for calculating engine design variables.
For example, a computer expresses a certain objective variable in quadratic polynomials of multiple design variables, and calculates using a genetic algorithm or other calculating methods for each of multiple combinations of multiple operating states. Thereby, it is possible to obtain local optimal solutions of design variables which minimize or maximize the multiple combinations of the objective variables.
Such local optimal solutions may not be combined as is for the purpose of calculating the global optimal solutions of design variables which minimize or maximize the multiple combinations of the objective variables in the entire operating range.
On the other hand, according to Japanese Unexamined Patent Application Publication No. Hei 11-353298, a method of calculating a comprehensive evaluated value by calculating a local preliminary evaluated value for each segmented evaluation area, and evaluating the values comprehensively, has been proposed for evaluating an engine and the like using a genetic algorithm online.
However, a method of optimizing a degree of change (smoothness) of design variables in relation to the change of operating states when calculating global optimal solutions of the design variables has not been disclosed in any way in Japanese Unexamined Patent Application Publication No. Hei 11-353298. More specifically, in the case of a design in which the design variables abruptly change in relation to a change in engine revolution speed and load, even the global optimal solutions are not preferable for the engine design, and therefore there is a need for obtaining global optimal solutions in which the degree of change is not abrupt but smooth.